acl.c

   1 /*
   2  * Copyright (C) 2005-2013 Andre Noll <maan@systemlinux.org>
   3  *
   4  * Licensed under the GPL v2. For licencing details see COPYING.
   5  */
   6
   7 /** \file acl.c Access control lists for paraslash senders. */
   8
   9 #include <netinet/in.h>
  10 #include <sys/socket.h>
  11 #include <regex.h>
  12 #include <arpa/inet.h>
  13 #include <sys/un.h>
  14 #include <netdb.h>
  15
  16 #include "para.h"
  17 #include "error.h"
  18 #include "string.h"
  19 #include "list.h"
  20 #include "net.h"
  21
  22 /**
  23  * Describes one entry in the blacklist/whitelist of a paraslash sender.
  24  */
  25 struct access_info {
  26         /** The address to be black/whitelisted. */
  27         struct in_addr addr;
  28         /** The netmask for this entry. */
  29         unsigned netmask;
  30         /** The position of this entry in the acl. */
  31         struct list_head node;
  32 };
  33
  34 /**
  35  * Return true if addr_1 matches addr_2 in the first `netmask' bits.
  36  */
  37 static int v4_addr_match(uint32_t addr_1, uint32_t addr_2, uint8_t netmask)
  38 {
  39         uint32_t mask = ~0U;
  40
  41         if (netmask < 32)
  42                 mask <<= (32 - netmask);
  43         return (htonl(addr_1) & mask) == (htonl(addr_2) & mask);
  44 }
  45
  46 /**
  47  * Find out whether the peer name of a given fd belongs to an acl.
  48  *
  49  * \param fd File descriptor.
  50  * \param acl The access control list.
  51  *
  52  * \return One if \a fd belongs to \a acl, zero otherwise.
  53  */
  54 static int acl_lookup(int fd, struct list_head *acl)
  55 {
  56         struct access_info *ai, *tmp;
  57         struct sockaddr_storage ss;
  58         socklen_t sslen = sizeof(ss);
  59         struct in_addr v4_addr;
  60
  61         if (getpeername(fd, (struct sockaddr *)&ss, &sslen) < 0) {
  62                 PARA_ERROR_LOG("Can not determine peer address: %s\n", strerror(errno));
  63                 goto no_match;
  64         }
  65         extract_v4_addr(&ss, &v4_addr);
  66         if (!v4_addr.s_addr)
  67                 goto no_match;
  68
  69         list_for_each_entry_safe(ai, tmp, acl, node)
  70                 if (v4_addr_match(v4_addr.s_addr, ai->addr.s_addr, ai->netmask))
  71                         return 1;
  72 no_match:
  73         return 0;
  74 }
  75
  76 /**
  77  * Add an entry to an access control list.
  78  *
  79  * \param acl The access control list.
  80  * \param addr The address to add.
  81  * \param netmask The netmask to use for this entry.
  82  */
  83 static void acl_add_entry(struct list_head *acl, char *addr, int netmask)
  84 {
  85         struct access_info *ai = para_malloc(sizeof(struct access_info));
  86
  87         inet_pton(AF_INET, addr, &ai->addr);
  88         ai->netmask = netmask;
  89         PARA_INFO_LOG("adding %s/%i to access list\n", addr, ai->netmask);
  90         para_list_add(&ai->node, acl);
  91 }
  92
  93 /**
  94  * Delete an entry from an access control list.
  95  *
  96  * \param acl The access control list.
  97  * \param addr The address to delete.
  98  * \param netmask The netmask of the entry to be removed from the list.
  99  */
 100 static void acl_del_entry(struct list_head *acl, char *addr, unsigned netmask)
 101 {
 102         struct access_info *ai, *tmp;
 103         struct in_addr to_delete;
 104
 105         inet_pton(AF_INET, addr, &to_delete);
 106
 107         list_for_each_entry_safe(ai, tmp, acl, node) {
 108
 109                 if (v4_addr_match(to_delete.s_addr, ai->addr.s_addr,
 110                                         PARA_MIN(netmask, ai->netmask))) {
 111                         PARA_NOTICE_LOG("removing %s/%i from access list\n",
 112                                         addr, ai->netmask);
 113                         list_del(&ai->node);
 114                         free(ai);
 115                 }
 116         }
 117 }
 118
 119 /**
 120  * Compute a string containing the contents of an acl.
 121  *
 122  * \param acl The access control list.
 123  *
 124  * \return A string containing the contents of \a acl, or \p NULL
 125  * if \a acl is empty.
 126  */
 127 char *acl_get_contents(struct list_head *acl)
 128 {
 129         struct access_info *ai, *tmp_ai;
 130         char *ret = NULL;
 131
 132         list_for_each_entry_safe(ai, tmp_ai, acl, node) {
 133                 char *tmp = make_message("%s%s/%d ", ret? ret : "",
 134                         inet_ntoa(ai->addr), ai->netmask);
 135                 free(ret);
 136                 ret = tmp;
 137         }
 138         return ret;
 139 }
 140
 141 /**
 142  * Initialize an access control list.
 143  *
 144  * \param acl The list to initialize.
 145  * \param acl_info An array of strings of the form ip/netmask.
 146  * \param num The number of strings in \a acl_info.
 147  */
 148 void acl_init(struct list_head *acl, char * const *acl_info, int num)
 149 {
 150         char    addr[16];
 151         int     mask, i;
 152
 153         INIT_LIST_HEAD(acl);
 154         for (i = 0; i < num; i++)
 155                 if (parse_cidr(acl_info[i], addr, sizeof(addr), &mask) == NULL)
 156                         PARA_CRIT_LOG("ACL syntax error: %s, ignoring\n",
 157                                       acl_info[i]);
 158                 else
 159                         acl_add_entry(acl, addr, mask);
 160 }
 161
 162 /**
 163  * Check whether the peer name of a given fd is allowed by an acl.
 164  *
 165  * \param fd File descriptor.
 166  * \param acl The access control list.
 167  * \param default_deny Whether \a acl is a whitelist.
 168  *
 169  * \return Positive if the peer of \a fd is permitted by \a acl, \p -E_ACL_PERM
 170  * otherwise.
 171  */
 172 int acl_check_access(int fd, struct list_head *acl, int default_deny)
 173 {
 174         int match = acl_lookup(fd, acl);
 175
 176         return (!match || default_deny) && (match || !default_deny)?
 177                 1 : -E_ACL_PERM;
 178 }
 179
 180 /**
 181  * Permit access for a range of IP addresses.
 182  *
 183  * \param addr The address to permit.
 184  * \param netmask The netmask of the entry to be permitted.
 185  * \param acl The access control list.
 186  * \param default_deny Whether \a acl is a whitelist.
 187  */
 188 void acl_allow(char *addr, int netmask,
 189                struct list_head *acl, int default_deny)
 190 {
 191         if (default_deny)
 192                 acl_add_entry(acl, addr, netmask);
 193         else
 194                 acl_del_entry(acl, addr, netmask);
 195 }
 196
 197 /**
 198  * Deny access for a range of IP addresses.
 199  *
 200  * \param addr The address to deny.
 201  * \param netmask The netmask of the entry to be denied.
 202  * \param acl The access control list.
 203  * \param default_deny Whether \a acl is a whitelist.
 204  */
 205 void acl_deny(char *addr, int netmask,
 206               struct list_head *acl, int default_deny)
 207 {
 208         acl_allow(addr, netmask, acl, !default_deny);
 209 }